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llvm-mirror/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sge-to-icmp-sle.ll
Sanjay Patel 5b68045419 [InstCombine] make icmp vector canonicalization safe for constant with undef elements
This is a fix for:
https://bugs.llvm.org/show_bug.cgi?id=43730
...and as shown there, we have existing test cases that show potential miscompiles.

We could just bail out for vector constants that contain any undef elements, or we can do as shown here:
allow the transform, but replace the undefs with a safe value.

For most of the tests shown, this results in a full splat constant (no undefs) which is probably a win
for further IR analysis because we conservatively don't match undefs in most cases. Codegen can probably
recover these kinds of undef lanes via demanded elements analysis if that's profitable.

Differential Revision: https://reviews.llvm.org/D69519
2019-10-29 10:58:14 -04:00

234 lines
6.9 KiB
LLVM

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -instcombine -S | FileCheck %s
; https://bugs.llvm.org/show_bug.cgi?id=38123
; Pattern:
; x & C s>= x
; Should be transformed into:
; x s<= C
; Iff: isPowerOf2(C + 1)
; C must not be -1, but may be 0.
; ============================================================================ ;
; Basic positive tests
; ============================================================================ ;
define i1 @p0(i8 %x) {
; CHECK-LABEL: @p0(
; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i8 [[X:%.*]], 4
; CHECK-NEXT: ret i1 [[TMP1]]
;
%tmp0 = and i8 %x, 3
%ret = icmp sge i8 %tmp0, %x
ret i1 %ret
}
; ============================================================================ ;
; Vector tests
; ============================================================================ ;
define <2 x i1> @p1_vec_splat(<2 x i8> %x) {
; CHECK-LABEL: @p1_vec_splat(
; CHECK-NEXT: [[TMP1:%.*]] = icmp slt <2 x i8> [[X:%.*]], <i8 4, i8 4>
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%tmp0 = and <2 x i8> %x, <i8 3, i8 3>
%ret = icmp sge <2 x i8> %tmp0, %x
ret <2 x i1> %ret
}
define <2 x i1> @p2_vec_nonsplat(<2 x i8> %x) {
; CHECK-LABEL: @p2_vec_nonsplat(
; CHECK-NEXT: [[TMP1:%.*]] = icmp slt <2 x i8> [[X:%.*]], <i8 4, i8 16>
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%tmp0 = and <2 x i8> %x, <i8 3, i8 15> ; doesn't have to be splat.
%ret = icmp sge <2 x i8> %tmp0, %x
ret <2 x i1> %ret
}
define <2 x i1> @p2_vec_nonsplat_edgecase(<2 x i8> %x) {
; CHECK-LABEL: @p2_vec_nonsplat_edgecase(
; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i8> [[X:%.*]], <i8 3, i8 0>
; CHECK-NEXT: [[RET:%.*]] = icmp sge <2 x i8> [[TMP0]], [[X]]
; CHECK-NEXT: ret <2 x i1> [[RET]]
;
%tmp0 = and <2 x i8> %x, <i8 3, i8 0>
%ret = icmp sge <2 x i8> %tmp0, %x
ret <2 x i1> %ret
}
define <3 x i1> @p3_vec_splat_undef(<3 x i8> %x) {
; CHECK-LABEL: @p3_vec_splat_undef(
; CHECK-NEXT: [[TMP1:%.*]] = icmp slt <3 x i8> [[X:%.*]], <i8 4, i8 4, i8 4>
; CHECK-NEXT: ret <3 x i1> [[TMP1]]
;
%tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 3>
%ret = icmp sge <3 x i8> %tmp0, %x
ret <3 x i1> %ret
}
; ============================================================================ ;
; One-use tests. We don't care about multi-uses here.
; ============================================================================ ;
declare void @use8(i8)
define i1 @oneuse0(i8 %x) {
; CHECK-LABEL: @oneuse0(
; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[X:%.*]], 3
; CHECK-NEXT: call void @use8(i8 [[TMP0]])
; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i8 [[X]], 4
; CHECK-NEXT: ret i1 [[TMP1]]
;
%tmp0 = and i8 %x, 3
call void @use8(i8 %tmp0)
%ret = icmp sge i8 %tmp0, %x
ret i1 %ret
}
; ============================================================================ ;
; Negative tests
; ============================================================================ ;
; Commutativity tests.
declare i8 @gen8()
define i1 @c0() {
; CHECK-LABEL: @c0(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[X]], 3
; CHECK-NEXT: [[RET:%.*]] = icmp sge i8 [[X]], [[TMP0]]
; CHECK-NEXT: ret i1 [[RET]]
;
%x = call i8 @gen8()
%tmp0 = and i8 %x, 3
%ret = icmp sge i8 %x, %tmp0 ; swapped order
ret i1 %ret
}
; ============================================================================ ;
; Rest of negative tests
; ============================================================================ ;
define i1 @n0(i8 %x) {
; CHECK-LABEL: @n0(
; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[X:%.*]], 4
; CHECK-NEXT: [[RET:%.*]] = icmp sge i8 [[TMP0]], [[X]]
; CHECK-NEXT: ret i1 [[RET]]
;
%tmp0 = and i8 %x, 4 ; power-of-two, but invalid.
%ret = icmp sge i8 %tmp0, %x
ret i1 %ret
}
define i1 @n1(i8 %x, i8 %y, i8 %notx) {
; CHECK-LABEL: @n1(
; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[X:%.*]], 3
; CHECK-NEXT: [[RET:%.*]] = icmp sge i8 [[TMP0]], [[NOTX:%.*]]
; CHECK-NEXT: ret i1 [[RET]]
;
%tmp0 = and i8 %x, 3
%ret = icmp sge i8 %tmp0, %notx ; not %x
ret i1 %ret
}
define <2 x i1> @n2(<2 x i8> %x) {
; CHECK-LABEL: @n2(
; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i8> [[X:%.*]], <i8 3, i8 16>
; CHECK-NEXT: [[RET:%.*]] = icmp sge <2 x i8> [[TMP0]], [[X]]
; CHECK-NEXT: ret <2 x i1> [[RET]]
;
%tmp0 = and <2 x i8> %x, <i8 3, i8 16> ; only the first one is valid.
%ret = icmp sge <2 x i8> %tmp0, %x
ret <2 x i1> %ret
}
; ============================================================================ ;
; Potential miscompiles.
; ============================================================================ ;
define i1 @nv(i8 %x, i8 %y) {
; CHECK-LABEL: @nv(
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[TMP0]], [[X:%.*]]
; CHECK-NEXT: [[RET:%.*]] = icmp sge i8 [[TMP1]], [[X]]
; CHECK-NEXT: ret i1 [[RET]]
;
%tmp0 = lshr i8 -1, %y
%tmp1 = and i8 %tmp0, %x
%ret = icmp sge i8 %tmp1, %x
ret i1 %ret
}
define <2 x i1> @n3_vec(<2 x i8> %x) {
; CHECK-LABEL: @n3_vec(
; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i8> [[X:%.*]], <i8 3, i8 -1>
; CHECK-NEXT: [[RET:%.*]] = icmp sge <2 x i8> [[TMP0]], [[X]]
; CHECK-NEXT: ret <2 x i1> [[RET]]
;
%tmp0 = and <2 x i8> %x, <i8 3, i8 -1>
%ret = icmp sge <2 x i8> %tmp0, %x
ret <2 x i1> %ret
}
define <3 x i1> @n4_vec(<3 x i8> %x) {
; CHECK-LABEL: @n4_vec(
; CHECK-NEXT: [[TMP0:%.*]] = and <3 x i8> [[X:%.*]], <i8 3, i8 undef, i8 -1>
; CHECK-NEXT: [[RET:%.*]] = icmp sge <3 x i8> [[TMP0]], [[X]]
; CHECK-NEXT: ret <3 x i1> [[RET]]
;
%tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 -1>
%ret = icmp sge <3 x i8> %tmp0, %x
ret <3 x i1> %ret
}
; Commutativity tests with variable
define i1 @cv0(i8 %y) {
; CHECK-LABEL: @cv0(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[X]], [[TMP0]]
; CHECK-NEXT: [[RET:%.*]] = icmp sge i8 [[TMP1]], [[X]]
; CHECK-NEXT: ret i1 [[RET]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
%tmp1 = and i8 %x, %tmp0 ; swapped order
%ret = icmp sge i8 %tmp1, %x
ret i1 %ret
}
define i1 @cv1(i8 %y) {
; CHECK-LABEL: @cv1(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[TMP0]], [[X]]
; CHECK-NEXT: [[RET:%.*]] = icmp sge i8 [[X]], [[TMP1]]
; CHECK-NEXT: ret i1 [[RET]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
%tmp1 = and i8 %tmp0, %x
%ret = icmp sge i8 %x, %tmp1 ; swapped order
ret i1 %ret
}
define i1 @cv2(i8 %y) {
; CHECK-LABEL: @cv2(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[X]], [[TMP0]]
; CHECK-NEXT: [[RET:%.*]] = icmp sge i8 [[X]], [[TMP1]]
; CHECK-NEXT: ret i1 [[RET]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
%tmp1 = and i8 %x, %tmp0 ; swapped order
%ret = icmp sge i8 %x, %tmp1 ; swapped order
ret i1 %ret
}